1. Field of Invention
The present invention relates to a road map display device adapted for use in a navigation apparatus for an automotive vehicle, and particularly to a road map display device in which a two-dimensional coordinate of road map data is converted into a trapezoid coordinate for display of a perspective view to display a road map near the present position of the vehicle in an expanded scale and to display a distant road map in a wide range.
2. Description of Related Art
In the publication of Japanese Patent No. 2869472 issued on Mar. 10, 1999, there has been proposed a road map display device in which a portion of a road map is displayed by coordinate conversion in perspective in the form of a projective view looked at from an ostensible view point located above the portion of the road map on the earth""s surface outside of a vehicle. In the road map display device, a projective conversion processing to a coordinate value of road map data is executed to convert road map data on a two-dimensional plane to data for display of a bird""s eye view and to project the coordinate value of the road map data on a display screen. Accordingly, in the road map display device, calculation of a trigonometric function is required in accordance with a look down angle, and three-dimensional calculation is required in consideration with the height of the view point. For this reason, the coordinate conversion processing of the road map data becomes complicated. This results in an increase of processing load of the road map and delay of conversion processing of the data for the bird"" eye view, causing difficulty in use of the display device.
To eliminate the difficulties described above, the present invention was made to provide a road map display device capable of rapidly converting a two-dimensional coordinate of road map data to a trapezoid coordinate for display of a perspective view by simple conversion processing without execution of complicated processing for coordinate convention so that a road map in a travel direction of an automotive vehicle is displayed in the form of a deep perspective view on a screen of a display unit.
According to the present invention, there is provided a road map display apparatus including a road map information memory for memorizing road map data on a two-dimensional coordinate, detection means for detecting a present position and a travel direction of an automotive vehicle, read-out means for reading out the two-dimensional coordinate of the road map from the information memory in accordance with the present position and travel direction of the vehicle detected by the detection means, and image display means for displaying the read out two-dimensional coordinate in the form of a plane view on a screen, wherein coordinate conversion means is provided to convert a square two-dimensional coordinate to a trapezoid coordinate for display of a perspective view on a two-dimensional plane in such a manner that an upper side of the two-dimensional coordinate is appropriately contracted relatively to a lower side of the two-dimensional coordinate, and wherein the read-out means is arranged to read out the two-dimensional coordinate of the road map data corresponding with a perspective view to be displayed on the screen of the image display means, wherein the coordinate conversion means is arranged to convert the two-dimensional coordinate read out by the read-out means to the trapezoid coordinate, and wherein the image display means is arranged to display the converted trapezoid coordinate in the form of a perspective view on the screen.
According to an aspect of the present invention, there is provided a road map display apparatus including a road map information memory for memorizing road map data on a two-dimensional coordinate; detection means for detecting a present position and a travel direction of an automotive vehicle, read-out means for reading out the two-dimensional coordinate of the road map data from the information memory in accordance with the present position and travel direction of the vehicle detected by the detection means, and image display means for displaying the read out two-dimensional coordinate in the form of a plane view on a display screen, wherein the road map display apparatus comprises parameter memory means for memorizing trapezoid conversion parameters preliminarily determined on a basis of a conversion formula for converting the two-dimensional coordinate of the road map data to a trapezoid coordinate for display of a perspective view in such a manner that an upper side of a square two-dimensional coordinate is contracted relatively to a lower side of the coordinate; and introduction means for obtaining the road map data included in a reverse trapezoid coordinate corresponding with a trapezoid coordinate defined by the trapezoid conversion parameters from the parameter memory means and for introducing the road map data into the trapezoid coordinate such that the road map data are displayed in the form of a perspective view on the screen of the image display means.
According to another aspect of the present invention, there is provided a road map display apparatus including a road map information memory for memorizing road map data on a two-dimensional coordinate, detection means for detecting a present position and a travel direction of an automotive vehicle, read-out means for reading out the two-dimensional coordinate of the road map from the information memory in accordance with the present position and travel direction of the vehicle detected by the detection means, and image display means for displaying the read out two-dimensional coordinate in the form of a plane view on a screen, wherein coordinate conversion means is provided to convert a square two-dimensional coordinate to a trapezoid coordinate for display of a perspective view on a two-dimensional plane in such a manner that an upper side of the two-dimensional coordinate is appropriately contracted relatively to a lower side of the two-dimensional coordinate in a condition where a diagonal line connecting one end of the upper side of the two-dimensional coordinate to the other end of the lower side of the two-dimensional coordinate is retained straight, wherein the read-out means is arranged to read out the two-dimensional coordinate of the road map data corresponding with a perspective view to be displayed on the screen of the image display means, and wherein the coordinate conversion means is arranged to convert the two-dimensional coordinate read out by the read-out means to the trapezoid coordinate so that the image display means displays the converted trapezoid coordinate in the form of a perspective view on the screen.
According to a further aspect of the present invention, there is provided a road map display apparatus including a road map information memory for memorizing road map data on a two-dimensional coordinate; detection means for detecting a present position and a travel direction of an automotive vehicle, read-out means for reading out the two-dimensional coordinate of the road map data from the information memory in accordance with the present position and travel direction of the vehicle detected by the detection means, and image display means for displaying the read out two-dimensional coordinate in the form of a plane view on a display screen, wherein the road map display apparatus comprises parameter memory means for memorizing trapezoid conversion parameters preliminarily determined on a basis of a conversion formula for converting the two-dimensional coordinate of the road map data to a trapezoid coordinate for display of a perspective view in such a manner that an upper side of a square two-dimensional coordinate is contracted relatively to a lower side of the coordinate in a condition where a diagonal line connecting one end of the upper side of the two-dimensional coordinate to the other end of the lower side of the two-dimensional coordinate is retained straight; and introduction means for obtaining the road map data included in a reverse trapezoid coordinate corresponding with a trapezoid coordinate defined by the trapezoid conversion parameters from the parameter memory means and for introducing the road map data into the trapezoid coordinate such that the road map data are displayed in the form of a perspective view on the screen of the image display means.
According to a another aspect of the present invention, there is provided a record media adapted for use in a road map display apparatus including a road map information memory for memorizing road map data on a two-dimensional coordinate; detection means for detecting a present position and a travel direction of an automotive vehicle, read-out means for reading out the two-dimensional coordinate of the road map data from the information memory in accordance with the present position and travel direction of the vehicle detected by the detection means, and image display means for displaying the read out two-dimensional coordinate in the form of a plane view on a display screen, wherein the record media is programmed to determine trapezoid conversion parameters on a basis of a conversion formula for converting the two-dimensional coordinate of the road map data to a trapezoid coordinate for display of a perspective view in such a manner that an upper side of a square two-dimensional coordinate is contracted relatively to a lower side of the coordinate and to read out the road map data included in a reverse trapezoid coordinate corresponding with a trapezoid coordinate defined by the trapezoid conversion parameters from the parameter memory means for introducing the road map data into the trapezoid coordinate such that the road map data are displayed in the form of a perspective view on the screen of the image display means.
In the road map display apparatus, the trapezoid conversion parameters preliminarily determined on a basis of the conversion formula are stored in the form of a table so that the two-dimensional coordinate obtained from the road map data can be converted to a trapezoid coordinate for display of a perspective view in a simple manner and that the road map data memorized in the road map information memory can be rapidly displayed in the form of a deep perspective view on the screen of the display unit.